EP1154139A2 - Regelung für einen Dieselmotor - Google Patents

Regelung für einen Dieselmotor Download PDF

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Publication number
EP1154139A2
EP1154139A2 EP01111467A EP01111467A EP1154139A2 EP 1154139 A2 EP1154139 A2 EP 1154139A2 EP 01111467 A EP01111467 A EP 01111467A EP 01111467 A EP01111467 A EP 01111467A EP 1154139 A2 EP1154139 A2 EP 1154139A2
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EP
European Patent Office
Prior art keywords
exhaust gas
target
value
engine
egr
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP01111467A
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English (en)
French (fr)
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EP1154139A3 (de
EP1154139B1 (de
Inventor
Hiroyuki Itoyama
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Nissan Motor Co Ltd
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Nissan Motor Co Ltd
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Filing date
Publication date
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Publication of EP1154139A2 publication Critical patent/EP1154139A2/de
Publication of EP1154139A3 publication Critical patent/EP1154139A3/de
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Publication of EP1154139B1 publication Critical patent/EP1154139B1/de
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D41/0047—Controlling exhaust gas recirculation [EGR]
    • F02D41/0065—Specific aspects of external EGR control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B37/00—Engines characterised by provision of pumps driven at least for part of the time by exhaust
    • F02B37/12—Control of the pumps
    • F02B37/24—Control of the pumps by using pumps or turbines with adjustable guide vanes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M47/00—Fuel-injection apparatus operated cyclically with fuel-injection valves actuated by fluid pressure
    • F02M47/02—Fuel-injection apparatus operated cyclically with fuel-injection valves actuated by fluid pressure of accumulator-injector type, i.e. having fuel pressure of accumulator tending to open, and fuel pressure in other chamber tending to close, injection valves and having means for periodically releasing that closing pressure
    • F02M47/027—Electrically actuated valves draining the chamber to release the closing pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D23/00—Controlling engines characterised by their being supercharged
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/02—EGR systems specially adapted for supercharged engines
    • F02M26/04—EGR systems specially adapted for supercharged engines with a single turbocharger
    • F02M26/05—High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/02—EGR systems specially adapted for supercharged engines
    • F02M26/09—Constructional details, e.g. structural combinations of EGR systems and supercharger systems; Arrangement of the EGR and supercharger systems with respect to the engine
    • F02M26/10—Constructional details, e.g. structural combinations of EGR systems and supercharger systems; Arrangement of the EGR and supercharger systems with respect to the engine having means to increase the pressure difference between the exhaust and intake system, e.g. venturis, variable geometry turbines, check valves using pressure pulsations or throttles in the air intake or exhaust system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/22—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
    • F02M26/23—Layout, e.g. schematics
    • F02M26/28—Layout, e.g. schematics with liquid-cooled heat exchangers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/22—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
    • F02M26/33—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage controlling the temperature of the recirculated gases
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/52—Systems for actuating EGR valves
    • F02M26/55—Systems for actuating EGR valves using vacuum actuators
    • F02M26/56—Systems for actuating EGR valves using vacuum actuators having pressure modulation valves
    • F02M26/57—Systems for actuating EGR valves using vacuum actuators having pressure modulation valves using electronic means, e.g. electromagnetic valves
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Definitions

  • This invention relates to control of a diesel engine equipped with a variable capacity turbocharger and an exhaust recirculation device.
  • Tokkai Hei 7-139413 published by the Japanese Patent Office in 1995 discloses a control method of a diesel engine equipped with a turbocharger and an exhaust gas recirculation (EGR) device.
  • the EGR device comprises an EGR valve which regulates an EGR amount.
  • the control method determines a turbocharging region and an EGR region according to a load and rotation speed of the engine.
  • EGR System in a Turbocharged Diesel Engine pp. 193 - 196, Technical Preprints, published by the Japan Institute of Automobile Technology in October, 1996, discloses control of the EGR amount of the EGR device by varying the opening area of the variable nozzle of the turbocharger.
  • the turbocharging pressure will vary, and when the turbocharging pressure is varied, the EGR amount will also vary because the exhaust pressure varies. That is, the turbocharging pressure and the EGR amount affect each other. Therefore, if it is attempted to keep the turbocharging pressure constant when varying the EGR amount, the opening of the variable nozzle of the turbocharger must be readjusted. Moreover, if it is attempted to keep the EGR amount constant when the turbocharging pressure is varied, the opening of the EGR valve must be readjusted.
  • the turbocharging pressure and the EGR amount affect the amount of noxious substances in the exhaust gas, so both the turbocharging pressure and the EGR amount must be controlled to optimum values in order to reduce the amount of noxious substances.
  • this invention provides a control device for an engine.
  • the engine comprises an intake passage, an exhaust passage and a turbocharger having an exhaust gas turbine in the exhaust passage, and an exhaust gas recirculation valve which recirculates part of an exhaust gas in the exhaust passage upstream of the exhaust gas turbine to the intake passage.
  • the turbocharger turbocharges an intake air in the intake passage according to a rotation of an exhaust gas turbine, and the exhaust gas turbine has an adjusting mechanism of a cross-sectional area of an exhaust gas flow in the exhaust gas turbine.
  • the control device comprises a sensor which detects a running condition of the engine, a sensor which detects the cross-sectional area, and a microprocessor programmed to determine a target recirculation amount of the exhaust gas recirculation valve according to the running condition, calculate a target control value of the exhaust gas recirculation valve based on the target recirculation amount and the cross-sectional area, and control the exhaust gas recirculation valve according to the target control value.
  • This invention also provides a control device comprising a mechanism for detecting a running condition of the engine, a mechanism for detecting the cross-sectional area, a mechanism for determining a target recirculation amount of the exhaust gas recirculation valve according to the running condition, a mechanism for calculating a target control value of the exhaust gas recirculation valve based on the target recirculation amount and the cross-sectional area, and a mechanism for controlling the exhaust gas recirculation valve according to the target control value.
  • This invention also provides control method for an engine comprising the steps of detecting a running condition of the engine, detecting the cross-sectional area, determining a target recirculation amount of the exhaust gas recirculation calculating a target control value of the exhaust gas recirculation valve based on the target recirculation amount and the cross-sectional area, and controlling the exhaust gas recirculation valve according to the target control value.
  • FIG. 1 is a schematic diagram of a control device for a diesel engine according to this invention.
  • FIG. 2 is a schematic diagram of a common rail fuel injection mechanism with which the diesel engine is provided.
  • FIG. 3 is a flowchart describing a routine for calculating a target fuel injection amount Qso /performed by a control unit according to this invention.
  • FIG. 4 is a diagram describing the contents of a basic fuel injection amount map stored by the control unit.
  • FIG. 5 is a flowchart describing a routine for calculating an EGR valve opening area Aev performed by the control unit.
  • FIG. 6 is a diagram describing the contents of an EGR valve lift amount map stored by the control unit.
  • FIG. 7 is a flowchart describing a routine for calculating a target EGR amount Tqec performed by the control unit.
  • FIG. 8 is a flowchart describing a routine for calculating a cylinder intake air amount Qac performed by the control unit.
  • FIG. 9 is a flowchart describing a routine for calculating an intake air flowrate Qas0 of the intake passage performed by the control unit.
  • FIG. 10 is a diagram describing the contents of an intake air volume map stored by the control unit.
  • FIG. 11 is a flowchart describing a routine for calculating a target EGR rate Megr performed by the control unit.
  • FIG. 12 is a diagram describing the contents of a map of a basic target EGR rate Megrb stored by the control unit.
  • FIG. 13 is a diagram describing the contents of a map of a water temperature correction coefficient Kegr_tw stored by the control unit.
  • FIG. 14 is a flowchart describing a complete combustion determining routine performed by the control unit.
  • FIG. 15 is a flowchart describing a routine for calculating a duty value Dtyvnt of a pressure control valve of a turbo supercharger performed by the control unit.
  • FIG. 16 is similar to FIG. 15, but showing a second embodiment of this invention.
  • FIG. 17 is a flowchart describing a routine for calculating an EGR rate Megrd of an intake valve position performed by the control unit.
  • FIG. 18 is a flowchart describing a routine for calculating a time constant equivalent value Kkin performed by the control unit.
  • FIG. 19 is a flowchart describing the contents of a map of a volume efficiency equivalent basic value Kinb performed by the control unit.
  • FIG. 20 is a flowchart describing a subroutine for calculating a target intake air amount tQac performed by the control unit.
  • FIG. 21 is a diagram describing the contents of a map of a target intake air amount basic value tQacb stored by the control unit.
  • FIG. 22 is a diagram describing the contents of a map of a correction factor ktQac stored by the control unit.
  • FIG. 23 is a diagram describing the contents of a map of a target intake air amount tQac stored by the control unit.
  • FIG. 24 is a flowchart describing a subroutine for calculating a real EGR amount Qec performed by the control unit.
  • FIG. 25 is a flowchart describing a routine for calculating a target opening Rvnt of a variable fuel injection nozzle performed by the control unit.
  • FIG. 26 is a diagram describing the contents of a map of the target opening Rvnt stored by the control unit.
  • FIG. 27 is similar to FIG. 25, but showing the second embodiment of this invention.
  • FIG. 28 is similar to FIG. 26, but showing the second embodiment of this invention.
  • FIG. 29 is a flowchart describing a routine for calculating an open loop control amount Avnt_f of the target opening performed by the control unit.
  • FIG. 30 is a flowchart describing a routine for calculating a feedback control amount Avnt_fb of the target opening performed by the control unit.
  • FIG. 31 is a flowchart describing a subroutine for performing linearization processing on the target opening performed by the control unit.
  • FIG. 32 is a diagram describing the contents of a map of the target opening Rvnt stored by the control unit.
  • FIG. 33 is a diagram describing a relation between an opening area of a variable nozzle, and a turbocharging pressure.
  • FIG. 34 is a flowchart describing a subroutine for setting the duty value Dtyvnt of the pressure control valve of the turbocharger performed by the control unit.
  • FIG. 35 is a flowchart describing a subroutine for setting a duty selection signal flag fvnt2 performed the control unit.
  • FIG. 36 is a flowchart describing a routine for correcting a temperature correction amount Dty_t of the duty value performed by the control unit.
  • FIG. 37 is a diagram describing the contents of a map of a basic exhaust gas temperature Texhb stored by the control unit.
  • FIG. 38 is a diagram describing the contents of a map of a water temperature correction coefficient Ktexh_ Tw stored by the control unit.
  • FIG. 39 is a diagram describing the contents of a map of the temperature correction amount Dty_t stored by the control unit.
  • FIG. 40 is a diagram describing the temperature characteristics of an actuator of the turbocharger.
  • FIG. 41 is a diagram of the contents of a map of a duty value Duty_h when the variable nozzle is fully closed, when the opening of the variable nozzle is constant or increasing, stored by the control unit.
  • FIG. 42 is a diagram of the contents of a map of a duty value Duty_I when the variable nozzle is fully open, when the opening of the variable nozzle is constant or increasing, stored by the control unit.
  • FIG. 43 is similar to FIG. 41, but showing a case where the opening of the variable nozzle is decreasing.
  • FIG. 44 is similar to FIG. 42, but showing a case where the opening of the variable nozzle is decreasing.
  • FIG. 45 is a diagram describing a hysteresis in the relation between a command opening linearization processing value and the duty value according to this invention.
  • FIG. 46 is a flowchart describing an operation check subroutine performed by the control unit.
  • FIG. 47 is a flowchart describing a routine for calculating the duty value Dtyvnt performed by the control unit.
  • FIG. 48 is a diagram describing the contents of a map of a control pattern value Duty_pu stored by the control unit.
  • FIG. 49 is a diagram describing the contents of a map of a duty value Duty_p_ne stored by the control unit.
  • FIG. 50 is a flowchart describing a subroutine for calculating an EGR amount feedback correction coefficients Kqac00 , an EGR flow velocity feedback correction coefficient Kqac0 , and an EGR flow velocity learning correction coefficient Kqac , performed by the control unit.
  • FIG. 51 is a flowchart describing a routine for setting a feedback permission flag fefb performed by the control unit.
  • FIG. 52 is a flowchart describing a routine for setting a learning value reflection permission flag felrn2 performed by the control unit.
  • FIG. 53 is a flowchart describing a routine for setting a learning permission flag felrn performed by the control unit.
  • FIG. 54 is a flowchart describing a routine for calculating the feedback correction coefficient Kqac00 performed by the control unit.
  • FIG. 55 is a diagram describing the contents of a map of a correction gain Gkfb of an exhaust gas recirculation flowrate stored by the control unit.
  • FIG. 56 is a diagram describing the contents of a map of a water temperature correction coefficient KgfbTw stored by the control unit.
  • FIG. 57 is a flowchart describing a routine for calculating the flow velocity feedback correction coefficient Kqac0 performed by the control unit.
  • FIG. 58 is a diagram describing the contents of a map of a correction gain Gkfbi of the exhaust gas recirculation flow velocity stored by the control unit.
  • FIG. 59 is a diagram describing the contents of a map of a water temperature correction coefficient KgfbiTw stored by the control unit.
  • FIG. 60 is a diagram describing the contents of a map of an error rate learning value Rqac n stored by the control unit.
  • FIG. 61 is a flowchart describing a routine for updating a learning value performed by the control unit.
  • FIG. 62 is a diagram describing the contents of a map of a learning rate Tclrn stored by the control unit.
  • FIG. 63 is a flowchart describing a routine for calculating a delay processing value RVNTE performed by the control unit.
  • FIG. 64 is a diagram describing the contents of a map of experimental values of an exhaust gas recirculation valve opening area per unit exhaust amount stored by the control unit.
  • FIG. 65 is similar to FIG. 64, but showing theoretical values.
  • a diesel engine 1 comprises an intake passage 3 and exhaust passage 3.
  • the diesel engine 1 is a multi cylinder diesel engine so constructed that the pattern of heat release is single stage combustion due to performing low temperature pre-mixture combustion.
  • Such a diesel engine is disclosed by Tokkai Hei 8-86251 published by the Japanese Patent Office in 1999.
  • Intake air of the intake air passage 3 is supplied to each cylinder of the diesel engine 1 via a collector 3A.
  • a swirl control valve is provided in an intake port leading from the intake passage 3 to each cylinder.
  • the swirl control valve closes part of the passage and sets up a swirl in the flow of air flowing into the combustion chamber of the diesel engine 1.
  • the combustion chamber comprises a large diameter toroidal combustion chamber.
  • This is a combustion chamber wherein a cylindrical cavity of the same diameter is formed on a piston from a cap surface to a base. A conical part is formed at the base of the cavity.
  • resistance to the swirl flowing in from the outside of the cavity is reduced, and mixing of air and fuel is promoted.
  • the swirl diffuses from the center of the cavity to the outside as the piston descends.
  • the diesel engine 1 comprises a common rail type fuel injection mechanism 10.
  • a fuel injection mechanism 10 comprises a fuel tank 11, fuel supply passage 12, supply pump 14, pressure accumulating chamber 16A formed in a common rail 16, and a nozzle 17 which is provided for every cylinder. After the fuel supplied from the supply pump 14 is stored in a pressure accumulator 16A via a high pressure fuel passage 15, it is distributed to each of the nozzles 17.
  • the nozzle 17 comprises a needle valve 18, nozzle chamber 19, fuel passage 20 to the nozzle chamber 19, retainer 21, hydraulic piston 22, return spring 23, fuel passage 24 which leads high pressure fuel to the hydraulic piston 22, and three-way solenoid valve 25 interposed in the fuel passage 24.
  • a check valve 26 and an orifice 27 are also provided in parallel in the fuel passage 24.
  • the return spring 23 pushes the needle valve 18 in the closing direction of the lower part of the figure via the retainer 21.
  • the hydraulic piston 22 comes in contact with the upper edge of the retainer 21.
  • the three-way valve 25 comprises a port A connected to the pressure accumulating chamber 16A, port B connected to the fuel passage 24 and port C connected to a drain 28.
  • ports A and Bare connected and ports B and C are shut off.
  • the fuel passages 20 and 24 are connected, and high pressure fuel is led to both the upper part of the hydraulic piston 22 and the nozzle chamber 19 from the pressure accumulating chamber 16A.
  • the pressure-receiving surface area of the hydraulic piston 22 is larger than the pressure -receiving surface area of the needle valve 18, in this state, the needle valve 18 sits in the valve seat, and the nozzle 17 is thereby closed.
  • fuel injection start timing is adjusted by the change-over timing from OFF to ON of the three-way valve 25, and fuel injection amount is adjusted by the duration of the ON state. Therefore, if the pressure of the pressure accumulating chamber 16A is the same, the fuel injection amount increases the longer the ON time of the three-way valve 25.
  • the fuel injection mechanism 10 comprises a return passage 13 which returns the surplus fuel discharged by the supply pump 14 to the fuel supply passage 12.
  • the return passage 13 is provided with a pressure regulating valve 31.
  • the pressure regulating valve 31 opens and closes the return passage 13, and adjusts the pressure of the pressure accumulating chamber 16A by varying the fuel injection amount to the pressure accumulating chamber 16A.
  • the fuel pressure of the pressure accumulating chamber 16A is equal to the fuel injection pressure of the nozzle 17, and the fuel injection rate is higher the higher the fuel pressure of the pressure accumulating chamber 16.
  • the three-way valve 25 and the pressure regulating valve 31 function according to the input signal from a control unit 41.
  • variable capacity turbocharger 50 comprises the exhaust gas turbine 52 and a compressor 55 which compresses air by the rotation of the exhaust gas turbine 52.
  • the compressor 55 is provided in the middle of the intake passage 3, and the intake passage 3 supplies air compressed by the compressor 55 to the diesel engine 1.
  • a variable nozzle 53 driven by a pressure actuator 54 is provided at an inlet to the exhaust gas turbine 52.
  • the pressure actuator 54 comprises a diaphragm actuator 59 which drives the variable nozzle 53 according to a signal pressure, and a pressure control valve 56 which generates the signal pressure according to a signal input from the control unit 41.
  • the control unit 41 controls the variable nozzle 53 to reduce the nozzle opening when the rotation speed of the diesel engine 1 is low. As a result, the flow velocity of exhaust gas introduced to the exhaust gas turbine 52 is increased so that a predetermined supercharging pressure is attained. On the other hand, the control unit 41 controls the variable nozzle 53 to fully open, when the rotation speed of the diesel engine 1 is high, in order to introduce exhaust gas into the exhaust gas turbine 52 without resistance.
  • the diesel engine 1 When the air-fuel mixture is burnt in the diesel engine 1, noxious nitrogen oxides (NOx) are formed. The NOx amount largely depends on the combustion temperature, and the generation amount of NOx can be suppressed by making the combustion temperature low.
  • This diesel engine 1 reduces the oxygen concentration in the combustion chamber by exhaust recirculation (EGR), and thereby realizes low-temperature combustion.
  • the diesel engine 1 comprises an exhaust gas recirculation (EGR) passage 4 which connects the exhaust passage 2 upstream of the exhaust gas turbine 52 and a collector 3A of the intake passage 3.
  • the EGR passage 4 is provided with a diaphragm type exhaust gas recirculation (EGR) valve 6 which responds to a control negative pressure provided from a negative pressure control valve 5 and a cooling system 7.
  • EGR exhaust gas recirculation
  • the negative pressure control valve 5 generates a negative pressure in response to a duty signal input from the control unit 41, and thereby varies the rate of exhaust gas recirculation (EGR rate) via the EGR valve 6.
  • the EGR rate is a maximum 100 percent, and as the rotation speed and load of the diesel engine 1 increase, the EGR rate is decreased.
  • the exhaust gas temperature is high, intake air temperature will rise if a large amount of EGR is performed. If the intake air temperature rises, NOx will no longer decrease, the ignition delay of injected fuel becomes shorter, and it becomes impossible to achieve pre-mixture combustion. Therefore, the EGR rate is made to decrease in stages as the rotation speed and load of the diesel engine 1 increase.
  • the cooling system 7 leads part of the engine cooling water to a water jacket 8 surrounding the EGR passage 4, and cools the recirculated exhaust gas in the EGR passage 4.
  • a cooling water inlet 7A of the water jacket 8 is provided with a flow control valve 9 which adjusts the recirculating amount of cooling water according to a signal from the control unit 41.
  • a pressure regulating valve 31, the three-way valve 25, the negative pressure control valve 5, a step motor 54 and the flow control valve 9 are respectively controlled by signals from the control unit 41.
  • the control unit 41 comprises a microcomputer equipped with a central processing unit (CPU), random access memory (RAM), read-only memory (ROM) and input/output interface (I/O interface).
  • Signals corresponding to detection values are input to the control unit 41 from a pressure sensor 32 which detects a fuel pressure of the pressure accumulating chamber 16A, an accelerator opening sensor 33 which detects an opening Cl of a vehicle accelerator pedal, a crank angle sensor 34 which detects a rotation speed Ne and crank angle of the diesel engine 1, a cylinder identifying sensor 35 which identifies cylinders of the diesel engine 1, a water temperature sensor 36 which detects a cooling water temperature Tw of the diesel engine 1, and an air flow meter 39 which detects an intake air flowrate of the intake passage 3 upstream of the compressor 55.
  • the control unit 41 calculates a target fuel injection amount of the nozzle 17 and target pressure of the pressure accumulating chamber 16A.
  • the fuel pressure of the pressure accumulating chamber 16A is feedback controlled by opening and closing the pressure regulating valve 31 so that the actual pressure of the pressure accumulating chamber 16A detected by the pressure sensor 32 coincides with the target pressure.
  • the control unit 41 also controls an ON time of the three-way valve 25 according to the calculated target fuel injection amount, and a fuel injection start timing in response to the running conditions of the diesel engine 1 by the change-over timing to ON of the three-way valve 25.
  • the fuel injection start timing is delayed near top dead center (TDC) of the piston so that the ignition delay of injected fuel is long. Due to this delay, the combustion chamber temperature at the time of ignition is lowered, and the generation of smoke due to the high EGR rate is suppressed by increasing the pre-mixture combustion ratio.
  • the injection start timing is advanced as the rotation speed and load of the diesel engine 1 increase. This is due to the following reason.
  • the ignition delay crank angle obtained by converting the ignition delay period increases in proportion to the increase in engine speed. Therefore, in order to fire the injected fuel at a predetermined crank angle, the injection start timing needs to be advanced at high rotation speed.
  • the control unit 41 also controls the turbocharging pressure and EGR amount.
  • the turbocharging pressure will also vary. Conversely if the turbocharging pressure is varied, as the exhaust gas pressure varies, the EGR amount varies. Therefore, the turbocharging pressure and EGR amount cannot be controlled independently, and may cause an external control disturbance to each other.
  • the opening of the variable nozzle 53 of the turbocharger 50 must be readjusted. Also, if it is attempted to keep the EGR amount constant when changing the turbocharging pressure, the opening of the EGR valve 6 must be readjusted. In such a method, it is difficult to ensure control precision during a transient state of the engine 1.
  • a control unit 41 calculates a target intake air amount tQac of an intake passage 3 according to vehicle running conditions, and sets a target opening Rvnt of a variable nozzle 53, which is an operating target value of a turbocharger 50, from a target intake air amount tQac , real EGR amount Qec of an EGR passage 4, and EGR rate Megrd of intake air passing through an intake valve of a diesel engine 1.
  • the EGR rate Megrd is also referred to as a real EGR rate.
  • a duty value Dtyvnt applied to a pressure control valve 56 is then determined using the routine shown in FIG. 15, and a corresponding command signal is output to the pressure control valve 56 so that the variable nozzle 53 attains the target opening Rvnt. In this way, the control unit 41 controls a turbocharging pressure of the turbocharger 50.
  • the control unit 41 also sets a target EGR amount Tqec based on a target EGR rate Megr and the running conditions of the vehicle. Further, a target EGR valve opening area Aev is calculated using the routine shown in FIG. 5 from the target EGR amount Tqec and a delay processing value RVNTE of the target opening Rvnt of the variable nozzle 53 of the turbocharger 50 and outputs a corresponding signal to the pressure control valve 5. In this way, the control unit 41 performs EGR control corresponding to the turbocharging pressure.
  • control unit 41 The above control performed by the control unit 41 will be described referring to the flowcharts. Of all the routines shown in the flowcharts, independent routines are performed at intervals which are described separately below, and subroutines are performed at the execution intervals of the parent routines.
  • FIG. 3, FIG. 4 and FIGs. 8-14 are known from Tokkai Hei 10-288071 published by the Japanese Patent Office in 1998.
  • the routine for calculating common parameters used for control of turbocharging pressure and the EGR amount will first be described.
  • the common parameters are a target fuel injection amount Qsol of a fuel injection device 10, a target EGR rate Megr of the EGR valve 6, a time constant equivalent value Kkin, a real EGR rate Megrd and a real intake air amount Qac.
  • the time constant equivalent value Kkin is a value representing an EGR control delay due to a collector 3A interposed between the EGR valve 6 and the intake valve of the diesel engine 1.
  • the real EGR rate Megrd shows the EGR rate of the intake air which passes through the intake valve of the diesel engine 1.
  • the real EGR rate Megrd varies with a first order delay relative to the target EGR rate Megr. The calculation of these parameters is performed independently of the turbocharging pressure control routine, and the EGR amount control routine.
  • This routine is performed in synchronism with a REF signal output by the crank angle sensor 34 for each reference position of the combustion cycle of each cylinder.
  • the REF signal is output every 180 degrees for a four cylinder engine, and every 120 degrees for a six cylinder engine.
  • step S1 the engine speed Ne is read, and in a step S2, the accelerator opening C / is read.
  • a basic fuel injection amount Mqdrv is calculated by looking up a map shown in FIG.4 based on the engine rotation speed Ne and the accelerator opening Cl. This map is stored beforehand in the memory of the control unit 41.
  • the target fuel injection amount Qsol is calculated by adding an increase correction based on an engine cooling water temperature Tw , etc., to the basic fuel injection amount Mqdrv.
  • the control unit 41 first reads the engine rotation speed Ne , the target fuel injection amount Qsol and the engine cooling water temperature Tw in a step S51.
  • the basic target EGR rate Megrb is calculated from the engine rotation speed Ne and the target fuel injection amount Qsol.
  • This map is stored beforehand in the memory of the control unit 41.
  • the basic target EGR rate Megrb is set larger in a region where the operating frequency of the engine is higher. This region corresponds to a region where both the rotation speed Ne and the load are small.
  • the load is represented by the target fuel injection amount Qsol ..
  • the basic target EGR rate Megrb is set to have small values.
  • a water temperature correction coefficient Kegr_Tw of the basic target EGR rate Megrb is calculated from the cooling water temperature Tw. This map is also stored beforehand in the memory of the control unit 41.
  • the target EGR rate Megr is calculated by the following equation (1) from the basic target EGR rate Megrb and water temperature correction coefficient Kegr_Tw.
  • Megr Megrb * Kegr _ Tw
  • a subroutine shown in FIG. 14 which determines whether or not the diesel engine 1 is in a complete combustion state, is performed.
  • step S61 the engine rotation speed Ne is read, and in a step S62, the engine rotation speed Ne and a complete combustion determining slice level NRPMK corresponding to a complete combustion rotation speed are compared.
  • the slice level NRPMK is set, for example, to 400rpm.
  • the routine proceeds to a step S63.
  • a counter value Tmrkb is compared with a predetermined time TMRKBP , and when the counter value Tmrkb is larger than the predetermined time TMRKBP , a complete combustion flag is turned ON in a step S64, and the subroutine is terminated.
  • the subroutine proceeds to a step S66.
  • the counter value Tmrkb is cleared to 0, the complete combustion flag is turned OFF in a next step S67, and the subroutine is terminated.
  • the control unit 41 determines the complete combustion flag in a step S56.
  • the complete combustion flag is ON
  • the subroutine of FIG. 11 is terminated.
  • the target EGR rate Megr is reset to 0 in a step S57, and the subroutine of FIG. 11 is terminated.
  • the real EGR rate Megrd varies with a first order delay relative to the target EGR rate Megr. As the calculations of the time constant equivalent value Kkin and the real EGR rate Megrd are inter-related, they will be described together.
  • FIG. 18 shows a routine for calculating the time constant equivalent value Kkin. This routine is performed in synchronism with the REF signal.
  • the control unit 41 reads the engine rotation speed Ne, the target fuel injection amount Qsol and the immediately preceding value Megrd n-1 (%) of the real EGR rate in a step S91.
  • the immediately preceding value Megrd n-1 is a value of Megrd calculated on the immediately preceding occasion when the routine was performed.
  • a volume efficiency equivalent basic value Kinb is calculated from the engine rotation speed Ne and the target fuel injection amount Qsol by looking up a map shown in FIG. 19 previously stored in the memory of the control unit 41.
  • a volume efficiency equivalent value Kin is calculated from the following equation (2).
  • EGR EGR
  • the proportion of Fresh air in the intake air falls, and the volume efficiency decreases. This reduction is reflected in the calculation of the volume efficiency equivalent value Kin via the volume efficiency equivalent basic value Kinb.
  • Kin Kinb ⁇ 1 1+ Megrd n-1 100
  • a step S94 the time constant equivalent value Kkin corresponding to the capacity of the collector 3A is calculated by multiplying the volume efficiency equivalent value Kin by a constant KVOL.
  • KVOL ( VE/NC ) /VM
  • FIG. 17 shows the routine for calculating the real EGR rate Megrd. This routine is performed at an interval of 10 milliseconds.
  • the control unit 41 first reads the target EGR rate Megr in a step S81.
  • the time constant equivalent value Kkin is read.
  • the routine of FIG. 18, which calculates the time constant equivalent value Kkin is performed in synchronism with the REF signal, and this routine which calculates the real EGR rate Megrd is performed at an interval of 10 milliseconds. Therefore, the time constant equivalent value Kkin read here is the time constant equivalent value Kkin calculated by the routine of FIG. 18immediately before the execution of the routine of FIG. 17. Likewise, the immediately preceding value Megrd n-1 of the real EGR rate read by the routine of FIG. 18 is the real EGR rate calculated by the routine of FIG. 17just before the execution of the routine of FIG. 18.
  • the real EGR rate Megrd is calculated from the following equation (4) using the target EGR rate Megr, immediately preceding value Megrd n-1 , and time constant equivalent value Kkin.
  • Ne* KE2# is a value to convert the EGR rate per intake stroke of each cylinder, to an EGR rate per unit time.
  • the real intake air amount Qac expresses the intake air amount in the intake valve position of one cylinder of the diesel engine 1.
  • the real intake air amount Qac is calculated from a flowrate Qas0 of the intake passage 3 detected by the air flow meter 39, but as the air flow meter 39 is situated upstream of the compressor 55, the real intake air amount Qac is calculated considering the time until the air which has passed through the air flow meter 39 is taken into the cylinder via the collector 3A.
  • control unit 41 reads the engine rotation speed Ne and intake air flowrate Qas0 of the intake passage 3.
  • a step S32 the intake air flowrate Qas0 is converted into an intake air amount Qac0 per cylinder by the following formula (5).
  • the constant KCON# is a constant for converting the intake air flowrate Qas0 of the intake passage 3 into the intake air amount per cylinder.
  • the constant KCON# is 30.
  • three cylinders perform air intake in each rotation, so the constant KCON# is 20.
  • control unit 41 performs the processing of steps S33, S34.
  • a value Qac0n-L of Qac0 which was calculated in the routine executed L times ago, is set as an intake air amount Qac n per cylinder at the inlet of the collector 3A.
  • the value of L is determined experimentally.
  • the real intake air amount Qac is calculated by equation (6) of first order delay.
  • Qac Qac n-1 ⁇ (1 - Kkin ) + Qac n ⁇ Kkin
  • the signal input into the control unit 41 from the air flow meter 39 is an analog voltage signal Us, and the control unit 41 converts the analog voltage signal Us into the intake air flowrate Qas0 of the intake passage 3 by the routine shown in FIG. 9. This routine is performed at an interval of 4 milliseconds.
  • the control unit 41 reads the analog voltage signal Us, and in a step S42, converts this into a flowrate Qas0_d by looking up a map shown in FIG. 10. This map is stored beforehand in the memory of the control unit 41.
  • a step S43 weighted average processing is performed on the flowrate Qas0_d , and the value obtained is taken as the intake air flowrate Qas0 of the intake passage 3.
  • the control of turbocharging pressure and control of the EGR amount corresponding to the turbocharging pressure performed by the control unit 41, are performed using the target fuel injection amount Qsol, time constant equivalent value Kkin , target EGR rate Megr, real EGR rate Megrd and the real intake air amount Qac calculated in this way.
  • the turbocharging pressure is controlled by a duty value Dtyvnt of a signal output to the pressure control valve 56 of the turbocharger 50.
  • Dtyvnt When the duty value Dtyvnt is zero, the pressure control valve 56 fully opens, and when the duty value is 1, it is fully closed.
  • the routine shown in FIG. 15 determines the duty value Dtyvnt. Therefore, this routine constitutes the main routine of turbocharging pressure control. This routine is performed at an interval of 10 milliseconds.
  • control unit 41 reads the real EGR rate Megrd in a step S71.
  • target intake air amount tQac is calculated using the subroutine shown in FIG. 20.
  • the control unit 41 reads the engine rotation speed Ne, target fuel injection amount Qsol and real EGR rate Megrd.
  • the real EGR rate Megrd is compared with a predetermined value MEGRLV#.
  • the predetermined value MEGRLV# is a value for determining whether or not exhaust gas recirculation is actually being performed, and is set to, for example, 0.5%.
  • step S102 when Megrd > MEGRLV# , the subroutine proceeds to a step S103. On the other hand, if Megrd ⁇ MEGRLV#, the subroutine proceeds to a step S106. In order to treat the case of a very small exhaust gas recirculation to be the same as the case where exhaust gas recirculation is not performed, the predetermined value MEGRLV# is not set to zero.
  • a target intake air amount basic value tQacb is calculated from the engine rotation speed Ne and real EGR rate Megrd by looking up a map shown in FIG. 21.
  • this map gives a larger target intake air amount basic value tQacb the larger the real EGR rate Megrd.
  • This map is previously stored in the memory of the control unit 41.
  • a correction coefficient ktQac of the target intake air amount is calculated from the engine rotation speed Ne and the target fuel injection amount Qsol by looking up a map shown in FIG. 22.
  • the correction coefficient ktQac is a coefficient for setting the target intake air amount according to the running condition of the vehicle.
  • the target intake air amount tQac is calculated by multiplying the target intake air amount basic value tQacb by the correction coefficient ktQac.
  • the target intake air amount tQac when exhaust gas recirculation is not performed is calculated from the engine rotation speed Ne and the target fuel injection amount Qsol by looking up a map shown in FIG. 23.
  • control unit 41 calculates the real EGR amount Qec which is the exhaust gas amount passing through the intake valve of the diesel engine 1 using the subroutine shown in FIG. 24.
  • the control unit 41 reads the intake air amount Qac n per cylinder at the inlet of the collector 3A, the target EGR rate Megr, and the time constant equivalent value Kkin corresponding to the collector capacity.
  • the intake air amount Qac n per cylinder at the inlet of the collector 3A a value calculated by the routine of FIG. 8 is used, and for the time constant equivalent value Kkin, a value calculated by the routine of FIG. 18 is used.
  • an EGR amount Qec0 per cylinder at the inlet of the collector 3A is calculated by the following equation (7).
  • Qec0 Qac n ⁇ Mger
  • the control unit 41 reads the target opening Rvnt of the variable nozzle 53.
  • the opening is a value which expresses the opening area of the variable nozzle 53 as a percentage relative to the opening area when the nozzle is fully open. Therefore, the opening when the nozzle is fully open is 100%, and the opening when it is fully closed is 0%.
  • the opening is used in order to express the opening of the variable nozzle 53 as a universal value which is not affected by the capacity of the turbocharger 50, but the opening area of the variable nozzle 53 may of course also be used.
  • the target opening Rvnt of the variable nozzle 53 is calculated by a routine shown in FIG. 25. This routine is performed independently of the main routine of FIG. 15 in synchronism with the REF signal.
  • a step S121 the control unit 41 first reads the target intake air amount tQac , real EGR amount Qec , engine rotation speed Ne and target fuel injection amount Qsol.
  • an intake air amount equivalent value tQas0 for calculating the target opening Rvnt of the variable nozzle 53 is calculated by the following equation (9).
  • an EGR amount equivalent value Qes0 is calculated by the following equation (10).
  • Qes0 ( Qec + Qsol ⁇ QFGAN# ) ⁇ Ne / KCON#
  • Ne/KCON# is a coefficient for converting the intake air amount per cylinder or the EGR amount into a value per unit time.
  • Qsol * QFGAN# is added to the target intake air amount tQac or the real EGR amount Qec in order to vary the target opening Rvnt according to the load of the diesel engine 1.
  • the effect of the target fuel injection amount Qsol which represents the load of the diesel engine 1, is adjusted by the gain QFGAN#.
  • tQas0 calculated in this way is referred to as an intake air amount equivalent value
  • Qes0 is referred to as a set EGR amount equivalent value.
  • the target opening Rvnt of the variable nozzle 53 is calculated by looking up a map shown in FIG. 26 stored beforehand based on the intake air amount equivalent value tQas0 and the EGR amount equivalent value Qes0. This map is stored beforehand in the memory of the control unit 41.
  • the target opening Rvnt decreases with increase of the EGR amount equivalent value Qes0. This is due to the following reason. Fresh air decreases as the EGR amount increases, and as a result, the air-fuel ratio becomes rich and smoke is easily generated. To avoid this situation, the target opening Rvnt is decreased and the fresh air intake amount is increased by raising the turbocharging pressure of the turbocharger 50 the more the EGR amount increases.
  • the turbocharging efficiency of the turbocharger 50 is small.
  • the target opening Rvnt is decreased as the intake air amount equivalent value tQas0 decreases. This is because the exhaust pressure required to rotate the exhaust gas turbine 52 is difficult to establish if the target opening Rvnt is increased in this region. It is also because, when the vehicle is accelerated by fully opening the accelerator pedal, the acceleration effect due to turbocharging is larger if the initial opening of the variable nozzle 53 is small.
  • the control unit 41 in a step S75, adds advance processing to the target opening Rvnt using the subroutine shown in FIG. 29.
  • This advance processing aims to compensate the operating delay based on the time required to operate the pressure actuator 54 which drives the variable nozzle 53. This processing is needed as the operation of the pressure actuator 54 using the pressure control valve 56 and the diaphragm actuator 59 has a large response delay compared to a step motor.
  • control unit 41 first reads the target opening Rvnt in a step S141.
  • an opening prediction value Cavnt n-1 calculated on the immediately preceding occasion when the subroutine was executed, is compared with the target opening Rvnt.
  • the opening prediction value Cavnt n-1 will be described in a later step S150.
  • the subroutine sets a advance correction gain Gkvnt as a predetermined value GKVNTO# , sets a advance correction time constant equivalent value Tcvnt as a predetermined value TCVNTO# in a step S144, and proceeds to the step S150.
  • time constant equivalent value Tcvnt is the inverse of a time constant, and shows that the response is faster for a larger value.
  • the subroutine determines whether or not Rvnt ⁇ Cavnt n-1 in a step S145.
  • the subroutine sets the advance correction gain Gkvnt to a predetermined value GKVNTC# in a step S146, sets the advance correction time constant equivalent value Tcvnt to a predetermined value TCVNTC# in a step S147, and proceeds to the step S150.
  • GKVNTO# ⁇ GKVNTC# and TCVNTO# ⁇ TCVNTC#.
  • a step S145 when the target opening Rvnt is not smaller than the opening prediction value Cavnt n-1 , i.e., Rvnt is equal to Cavnt n-1 , the subroutine sets the advance correction gain Gkvnt equal to the immediately preceding value Gkvnt n-1 in a step S148, sets the advance correction time constant equivalent value Tcvnt equal to the immediately preceding value Tcvnt n-1 , and proceeds to the step S150.
  • an opening prediction value Cavnt is calculated from the equation (11 below using the advance correction time constant equivalent value Tcvnt and the target opening Rvnt.
  • an open loop control amount Avnt_f of the target opening is calculated by the following equation (12) using the opening prediction value Cavnt and the target opening Rvnt.
  • Avnt_f Gkvnt ⁇ Rvnt - ( Gkvnt - 1) ⁇ Cavnt n-1
  • control unit 41 After executing the subroutine of FIG. 29, the control unit 41 returns to the routine of FIG. 15, and calculates a feedback correction amount Avnt_fb of the target opening Rvnt using the subroutine shown in FIG. 30 in a step S76.
  • control unit 41 first reads the target intake air amount tQac , target EGR rate Megr, engine rotation speed Ne, target fuel injection amount Qsol and the real intake air amount Qac in a step S161.
  • the target EGR rate Megr is compared with the predetermined value MEGRLV#.
  • the predetermined value MEGRLV# is the same as that which was used in the step S102 of FIG. 20.
  • it is determined whether or not to perform exhaust gas recirculation by comparing the target EGR rate Megr with the predetermined value MEGRLV#.
  • Megr ⁇ MEGRLV# is a region where exhaust gas recirculation should be performed.
  • the subroutine proceeds to a step S164, and an error rate dQac of the target intake air amount tQac is calculated relative to the real intake air amount Qac by the following equation (13).
  • dQac ( tQac/Qac ) - 1
  • the error rate dQac takes a positive value
  • the error rate dQac takes a negative value
  • the error rate dQac is zero.
  • Megr ⁇ MEGRLV# is a region in which exhaust gas recirculation is not performed.
  • the subroutine sets the error rate dQac to 0 in a step S163.
  • a feedback gain correction coefficient Kh used for feedback control of the target opening Rvnt is calculated, from the engine rotation speed Ne and the target fuel injection amount Qsol , by looking up a map stored beforehand in the control unit 41.
  • the map is set so as to increase the correction coefficient Kh the larger the load of the diesel engine 1 represented by the target fuel injection amount Qsol , and the larger the rotation speed Ne of the diesel engine 1.
  • a proportional feedback gain Kp , integral feedback gain Ki and differential feedback gain Kd are calculated by multiplying the correction coefficient Kh by a proportion constant KPB# , integral constant KIB# and differential constant KDB# , respectively.
  • the feedback control amount Avnt_fb of the target opening Rvnt of the variable nozzle 53 is calculated using proportional/integral/differential control equations known in the art.
  • control unit 41 After the above calculation, the control unit 41 returns to the routine of FIG. 15, and performs linearization processing on the target opening Rvnt using a subroutine shown in FIG. 31 in a step S77.
  • the control unit 41 reads the open loop control amount Avnt_f and the feedback control amount Avnt_fb of the target opening Rvnt.
  • a command opening Avnt is calculated by summing these control amounts.
  • a linearization processing value Ratdty of the command opening Avnt is calculated from the command opening Avnt by looking up a map of FIG. 32 previously stored in the memory of the control unit 41.
  • control unit 41 returns again to the routine of FIG. 15, and determines the duty value Dtyvnt using a subroutine shown in FIG. 34 in a step S78.
  • FIG. 33 shows the characteristics of the opening area of the variable nozzle 53 with respect to the turbocharging pressure.
  • the characteristics when EGR is performed is indicated by a curve w/ EGR and the characteristics when EGR is not performed is indicated by another curve w/o EGR.
  • the turbocharging pressure is high, or the intake air amount is large, the variation of the opening area of the variable nozzle 53 relative to the variation of the turbocharging pressure is small.
  • the opening area of the variable nozzle 53 largely varies with respect to the variation of the turbocharging pressure. EGR further promotes this tendency. In other words, if the opening area of the variable nozzle 53 is controlled with a fixed feedback gain, it is difficult to control precisely the turbocharging pressure. In order to ensure the prompt response of the turbocharging pressure, the feedback gain Kh must be set to vary according to running conditions.
  • the control unit 41 reads the engine rotation speed Ne, target fuel injection amount Qsol , linearization processing value Ratdty of the command opening, advance correction time constant equivalent value Tcvnt and cooling water temperature Tw of the diesel engine 1.
  • duty signal variation flags are set using the subroutine shown in FIG. 35.
  • control unit 41 first reads the command opening Avnt and the advance correction time constant equivalent value Tcvnt in a step S201.
  • a command opening prediction value Adlyvnt is calculated by the following equation (14).
  • the relation between the command opening Avnt and the command opening prediction value Adlyvnt corresponds to the relation between the target opening Rvnt and the opening prediction value Cavnt.
  • step S203 the command opening prediction value Adlyvnt is compared with a command opening prediction value Adlyvnt n-M calculated by the subroutine executed M times ago.
  • the subroutine sets an operation direction flag fvnt to 1 in a step S204, and proceeds to a step S206.
  • a duty hold flag fvnt2 is set to 1, and the subroutine is terminated.
  • Adlyvnt ⁇ Adlyvnt n-M in the step S203 it shows that the command opening is decreasing.
  • the subroutine resets the operation direction flag fnvt to zero in a step S205, and the routine proceeds to the step S208.
  • step S208 the duty hold flag fvnt2 is reset to zero, and the subroutine is terminated.
  • the control unit 41 reads a duty value temperature correction amount Dty_t in a step S183 of FIG. 34.
  • the duty value temperature correction amount Dty_t is calculated by a routine of FIG. 36 performed independently in synchronism with the REF signal.
  • control unit 41 first reads the engine rotation speed Ne, target fuel injection amount Qsol and cooling water temperature Tw.
  • a basic exhaust gas temperature Texhb is calculated from the engine rotation speed Ne and target fuel injection amount Qsol by looking up a map shown in FIG. 37 previously stored in the memory of the control unit 41.
  • the basic exhaust gas temperature Texhb is the exhaust gas temperature after the diesel engine 1 has completed warming up.
  • a water temperature correction coefficient Ktexh_Tw is calculated by looking up a map shown in FIG. 38 stored in the control unit 41, based on the cooling water temperature Tw.
  • an exhaust gas temperature Texhi is calculated by multiplying the basic exhaust gas temperature Texhb by the water temperature correction coefficient Ktexh_Tw.
  • a real exhaust gas temperature Texhdly is calculated by adding a first order processing delay to the exhaust gas temperature Texhi by the following equation (15). This value is a value which takes account of the delay due to the heat inertia in the variation of exhaust gas temperature.
  • Texhdly Texhi ⁇ KEXH# + Texhdly n-1 ⁇ (1 - KEXH# ) where,
  • a difference dTexh of the basic exhaust gas temperature Texhb and this real exhaust gas temperature Texhdly is calculated.
  • a last step S217 the duty value temperature correction amount Dty_t is calculated by looking up a map shown in FIG. 39 previously stored in the memory of the control unit 41, based on the difference dTexh. The meaning of the processing of the steps S216 and S217 will be described in detail later.
  • Steps S184-S189 are steps which add hysteresis processing to the duty value.
  • the control unit 41 determines the operation direction flag fvnt in the step S184.
  • the operation direction flag fvnt is 1, i.e., when the command opening Avnt is increasing or constant
  • the processing of steps S185, S186 is performed.
  • a duty value Duty_h when the variable nozzle 53 is fully closed is calculated based on the target fuel injection amount Qsol by looking up a Duty_h_p map shown in FIG. 41.
  • a duty value Duty_I when the variable nozzle 53 is fully open is calculated by looking up a Duty_I_p map shown in FIG. 42. After this processing, the subroutine proceeds to a step S189.
  • step S187 the duty value Duty_h when the variable nozzle 53 is fully closed, is calculated based on the target fuel injection amount Qsol by looking up a Duty_h_n map shown in FIG. 43.
  • step S188 the duty value Duty_I when the variable nozzle 53 is fully open, is calculated based on the target fuel injection amount Qsol by looking up a Duty_I_n map shown in FIG. 44.
  • a command duty basic value Dty_h is calculated by performing linear interpolation processing using the duty values Duty_h, Duty_I found by the above processing, the linearization processing value Ratdty of the command opening Avnt , and the temperature correction amount Dty_t.
  • the command duty basic value Dty_h is made smaller, for the same linearization processing value Ratdty , in the case where the command opening Avnt is decreasing than in other cases.
  • the duty hold flag fvnt2 is determined.
  • a command duty value Dtyv is set equal to the duty value Dtyvnt n-1 calculated on the immediately preceding occasion the subroutine was executed, in a step S191.
  • the duty value Dtyvnt n-1 will be described in detail later.
  • the command duty value Dtyv is set equal to the command duty basic value Dty_h calculated in the step S189.
  • control unit 41 After determining the command duty value Dtyv in the step S191 or step S192, in a final step S193, the control unit 41 performs an operation check on the variable nozzle 53 using the subroutine of FIG. 46 based on the command duty value Dtyv .
  • control unit 41 first reads the command duty value Dtyv, engine rotation speed Ne, target fuel injection amount Qsol and the cooling water temperature Tw.
  • step S222 it is determined whether or not the target fuel injection amount Qsol is less than a predetermined value QSOLDIZ#. When this condition is satisfied, it means that the diesel engine 1 is performing fuel cut.
  • step S223 it is determined whether or not the engine rotation speed Ne is less than a predetermined value NEDIZ#. When this condition is satisfied, it means that the rotation speed Ne of the diesel engine 1 is in an intermediate or low speed region.
  • step S224 it is determined whether or not the cooling water temperature Tw is less than a predetermined value TwDIZ#. When this condition is satisfied, it means that warming up of the diesel engine 1 is not complete.
  • step S225 it is determined whether or not an operation check flag Fdiz is 0. When this condition is satisfied, it means that an operation check has not yet been performed.
  • an operation check counter value CtFdiz is incremented in a step S226, and the routine proceeds to a step S227.
  • the subroutine If any of the determination results of the steps S222-S224 is not satisfied, the subroutine resets the operation check flag Fdiz to 0 in a step S233, and proceeds to a step S234. However, when the operation check flag Fdiz is 1 in the step S225, it proceeds to the step S234 immediately.
  • a step S227 the operation check counter value CtFdiz is compared with a predetermined upper limiting value CTRDIZH#.
  • a step S2208 the operation check counter value CtFdiz is compared with a predetermined lower limiting value CTRDIZL#.
  • a duty value Dtyvnt is set for checking operation using a subroutine shown in FIG. 47.
  • the upper limiting value CTRDIZH# is set to, for example, 7 seconds
  • the lower limiting value CTRDIZL# is set to, for example, 2 seconds.
  • the duty value for checking operation is set only in a 5 second interval of the difference between the upper limiting value and lower limiting value.
  • the control unit 41 in a step S241, first reads the operation check counter value CtFdiz and engine rotation speed Ne.
  • a control pattern value Duty_pu is set by looking up a map shown in FIG. 48based on the difference of the operation check counter value CtFdiz and lower limiting value CTRDIZL#. This map is previously stored in the memory of the control unit 71 The control pattern value Duty_pu is set so that it repeatedly varies between 0 and 1 with a short period according to the elapsed time after the operation check counter value CtFdiz exceeds the lower limiting value CTRDIZL#.
  • a duty value Duty_p_ne commanded to the pressure control valve 56 is calculated by looking up a map shown in FIG. 49 previously stored in the memory of the control unit 41, based on the engine rotation speed Ne.
  • the duty value Duty_p_ne is set supposing that the duty for checking the opening and closing operation of the variable nozzle 53 differs according to the engine rotation speed Ne . For example, when the variable nozzle 53 is to be closed, it must close against the exhaust gas pressure. The exhaust gas pressure increases in accordance with the increase in engine rotation speed Ne.
  • the duty value Duty_p_ne is decreased as the engine rotation speed Ne increases so as to reduce the impact on the engine running environment.
  • step S244 the duty value Dtyvnt is calculated by multiplying the duty value Duty_p_ne by the control pattern value Duty_pu , and the subroutine is terminated.
  • step S227 of FIG. 46 when the operation check counter value CtFdiz is not less than the upper limiting value CTRDIZH# , the processing of the step S230 is performed.
  • an immediately preceding value CtFdiz n-1 of the operation check counter value CtFdiz operation is compared with the upper limiting value CTRDIZH#.
  • the duty value Dtyvnt is set to 0 in a step S231
  • the operation check flag Fdiz is set to 1 in a step S232, and the subroutine is terminated.
  • variable nozzle 53 By once setting the duty value Dtyvnt to 0 in the step S231when the operation check is completed, the variable nozzle 53 fully opens. This operation aims to maintain control precision during ordinary control performed thereafter. By setting the operation check flag Fdiz to 1, the determination result of the step S225 will always be negative in the execution of the subroutine thereafter. It means the operation check of the variable nozzle 53 is performed only once after starting the diesel engine 1.
  • the subroutine proceeds to the step S234.
  • the operation check counter value CtFdiz is reset to 0, and the routine proceeds to a step S235.
  • the subroutine When the operation check counter value CtFdiz is less than the predetermined lower limiting value CTRDIZL# in the step S228 , the subroutine also proceeds to the step S235.
  • step S235 the duty value Dtyvnt for operation check is set equal to the command duty value Dtyv determined in the step S191 or step S192, and the subroutine is terminated. In this case therefore, the ordinary control of the variable nozzle 53 is performed.
  • This routine constitutes the main feature of this invention. This routine is performed every time the REF signal is input.
  • control unit 41 calculates a target EGR amount Tqec of the EGR valve 6 using a subroutine shown in FIG. 7.
  • the control unit 41 reads the intake air amount Qac n per cylinder at the inlet of the collector 3A.
  • Qac n is a value calculated in the above-mentioned step S33 of FIG. 8.
  • the target EGR rate Megr is read.
  • the target EGR rate Megr is a value calculated by the routine of FIG. 11.
  • a required EGR amount Mqec is calculated by the following equation (16).
  • Mqec Qac n ⁇ Megr
  • a next step S24 delay processing is performed on the required EGR amount Mqec by the following equation (17), using the time constant equivalent value Kkin calculated by the routine of FIG. 18, to convert it to an intermediate value Rqec corresponding to the required EGR amount per cylinder in the intake valve position of the diesel engine 1.
  • the target EGR amount Tqec per cylinder in the position of the EGR valve 6 is calculated by performing advance processing by the following equation (18) using the intermediate value Rqec and the required EGR amount Mqec.
  • the control unit 41 calculates the EGR flow velocity feedback correction coefficient Kqac0 , the EGR amount feedback correction coefficient Kqac00 , and the EGR flow velocity learning correction coefficient Kqac , using a subroutine of FIG. 50.
  • the control unit 41 first reads the target intake air amount tQac , real intake air amount Qac , engine rotation speed Ne and target fuel injection amount Qsol.
  • a delay processing value tQacd of the target intake air amount tQac is calculated using the following equation (19), from the target intake air amount tQac and the time constant equivalent value Kkin calculated by the routine of FIG. 8. This value corresponds to the target intake air amount in the intake valve position of the diesel engine 1.
  • tQacd tQac ⁇ Kkin ⁇ KQA# + tQacd n-1 ⁇ (1 - Kkin ⁇ KQA# ) where,
  • a feedback permission flag fefb a learning permission flag felrn and a learning value reflection permission flag felrn2 which are related to the control of the EGR valve opening are read.
  • FIG. 51 shows the routine for setting the feedback permission flag fefb. This routine is performed at an interval of 10 milliseconds.
  • the control unit 41 reads the engine rotation speed Ne, target fuel injection amount Qsol, real EGR rate Megrd and water temperature Tw.
  • step S272 it is determined whether or not the real EGR rate Megrd exceeds a predetermined value MEGRFB#.
  • the predetermined value MEGRFB# is a value for checking that exhaust gas recirculation is actually performed.
  • step S273 it is determined whether or not the cooling water temperature Tw exceeds a predetermined value TwFBL#.
  • the predetermined value TwFBL# is set to 30'C.
  • step S274 it is determined whether or not the target fuel injection amount Qsol exceeds a predetermined value QSOLFBL#.
  • the predetermined value QSOLFBL# is a value for checking that the diesel engine 1 is not in a fuel cut state.
  • the predetermined value NeFBL# is a value for checking that the vehicle is not in a low-speed region where the diesel engine 1 stops rotation.
  • step S272-S275 When all of the conditions of step S272-S275 are satisfied, the subroutine proceeds to a step S276 and increments a timer value Ctrfb.
  • a following step S278 it is determined whether or not the timer value Ctrfb is greater than a predetermined value TMRFB#.
  • the predetermined value TMRFB# is set to, for example, a value less than 1 second.
  • the subroutine sets the feedback permission flag fefb to 1 in a step S279, and the subroutine is terminated.
  • the subroutine resets the timer value Ctrfb to 0, and proceeds to a following step S280.
  • step S278 When the determination of the step S278 is negative, the subroutine also proceeds to the step S280.
  • step S280 the feedback permission flag fefb is reset to 0 and the subroutine is terminated.
  • the feedback permission flag fefb is set to 1 only when the state where all of the conditions of the steps S272-S275 were satisfied, continues for a time exceeding the predetermined value TMRFB#, and in other cases, the feedback permission flag fefb is reset to 0.
  • FIG. 52 shows a routine for setting the learning value reflection permission flag felrn2. This routine is also performed at an interval of 10 milliseconds.
  • the control unit 41 reads the engine rotation speed Ne, target fuel injection amount Qsol , real EGR rate Megrd and cooling water temperature Tw.
  • step S292 it is determined whether or not the real EGR rate Megrd exceeds a predetermined value MEGRLN2#.
  • the predetermined value MEGRLN2# is a value for checking that exhaust gas recirculation is actually performed.
  • step S293 it is determined whether or not the cooling water temperature Tw exceeds a predetermined value TwLNL2#.
  • the predetermined value TwLNL2# is set to 20'C.
  • step S294 it is determined whether or not the target fuel injection amount Qsol exceeds a predetermined value QSOLLNL2#.
  • the predetermined value QSOLLNL2# is a value for checking that the diesel engine 1 is not in a fuel cut state.
  • step S295 it is determined whether or not the engine rotation speed Ne exceeds a predetermined value NeLNL2#.
  • the predetermined value NeLNL2# is a value for checking that the vehicle is not in a low-speed region where the diesel engine 1 stops rotation.
  • step S292-S295 Only when all of the conditions of step S292-S295 are satisfied, the subroutine proceeds to a step S296 and increments a timer value Ctrln2.
  • step S298 it is determined whether or not the timer value Ctrln2 exceeds a predetermined value TMRLN2#.
  • the predetermined value TMRLN2# is set to 0.5 seconds.
  • the subroutine sets the learning value reflection permission flag felrn2 to 1 in a step S299, and the subroutine is terminated.
  • step S297 the subroutine resets the timer value Ctrln2 to 0, and proceeds to a following step S300.
  • step S298 the determination of the step S298 is negative, the subroutine also proceeds to the step S300.
  • step S300 the learning value reflection permission flag felrn2 is reset to 0 and the subroutine is terminated.
  • FIG. 53 shows the routine for setting the learning permission flag felrn. This routine is also performed at an interval of 10 milliseconds.
  • the control unit 41 reads the engine rotation speed Ne, target fuel injection amount Qsol, real EGR rate Megrd, and water temperature Tw.
  • step S312 it is determined whether or not the real EGR rate Megrd exceeds a predetermined value MEGRLN#.
  • the predetermined value MEGRLN# is a value for checking that exhaust gas recirculation is actually performed.
  • step S313 it is determined whether or not the cooling water temperature Tw exceeds a predetermined value TwLNL#.
  • the predetermined value TwLNL# is set to 70-80'C.
  • the predetermined value QSOLLNL# is a value for checking that the diesel engine 1 is not in a fuel cut state.
  • step S315 it is determined whether or not the engine rotation speed Ne exceeds a predetermined value NeLNL#.
  • the predetermined value NeLNL# is a value for checking that the vehicle is not in a low-speed region where the diesel engine 1 stops rotation.
  • step S316 it is determined whether or not the feedback permission flag fefb is 1.
  • step S317 it is determined whether or not the learning value reflection permission flag felrn2 is 1.
  • a following step S320 it is determined whether or not the timer value Ctrln exceeds a predetermined value TMRLN#.
  • the predetermined value TMRLN# is set to 4 seconds.
  • the subroutine sets the learning permission flag felrn to 1 in a step S321, and the subroutine is terminated.
  • the subroutine resets the timer value Ctrln to 0, and proceeds to a following step S322.
  • the subroutine also proceeds to the step S322 when the determination of the step S320 is negative. In the step S322, the learning permission flag felrn is reset to 0, and the subroutine is terminated.
  • control unit 41 determines whether or not the feedback permission flag fefb is 1.
  • the control unit 41 proceeds to a step S259.
  • the control unit 41 sets the feedback correction coefficient Kqac00 of the EGR amount to 1 in a step S257, sets the feedback correction coefficient Kqac0 of the EGR flow velocity to 1 in a following step S258, and then proceeds to the step S259.
  • the calculation of the feedback correction coefficient Kqac00 of the EGR amount is performed by a subroutine of FIG. 54.
  • the control unit 41 first reads the delay processing value tQacd of the target intake air amount, real intake air amount Qac , engine rotation speed Ne, target fuel injection amount Qsol and the cooling water temperature Tw.
  • the delay processing value tQacd is a value calculated in the step S252 of FIG. 50.
  • a correction gain Gkfb of the EGR flowrate is calculated by looking up a map shown in FIG. 55 previously stored in the memory of the control unit 41, based on the engine rotation speed Ne and the target fuel injection amount Qsol.
  • a water temperature correction coefficient KgfbTw of the correction gain is calculated by looking up a map shown in FIG. 56 previously stored in the memory of the control unit 41, based on the cooling water temperature Tw.
  • the feedback correction coefficient Kqac00 of the EGR amount is calculated by the following equation (20), using the correction gain Gkfb and the water temperature correction coefficient KgfbTw.
  • Kqac00 ( tQacd/ Qac- 1) ⁇ Gkfb ⁇ Kgfbtw + 1
  • the feedback correction coefficient Kqac00 of the EGR amount is a value centered on 1. According to equation (20), the feedback correction coefficient Kqac00 of the EGR amount is determined to be proportional to the error ratio of the delay processing value tQacd of the target intake air amount.
  • the calculation of the feedback correction coefficient Kqac0 of the EGR flow velocity is performed by a subroutine shown in FIG. 57.
  • the control unit 41 first reads the delay processing value tQacd of the target intake air amount, real intake air amount Qac , engine rotation speed Ne, target fuel injection amount Qsol and the cooling water temperature Tw.
  • a correction gain Gkfbi of the EGR flow velocity is calculated by looking up a map shown in FIG. 58 previously stored in the memory of the control unit 41, based on the engine rotation speed Ne and the fuel injection amount Qsol.
  • a water temperature correction coefficient KgfbiTw of the correction gain is calculated by looking up a map shown in FIG. 59 previously stored in the memory of the control unit 41, based on the cooling water temperature Tw.
  • an error ratio Rqac0 is calculated by the following equation (21), using the correction gain Gkfbi and the water temperature correction coefficient KgfbiTw.
  • step S245 by adding 1 to the error ratio Rqac0 , the EGR flow velocity feedback correction coefficient Kqac0 is calculated. Therefore, the feedback correction coefficient Kqac0 of the EGR flow velocity is a value proportional to the integral of the error ratio.
  • the control unit 41 determines whether or not the learning value reflection permission flag felrn2 is 1.
  • the control unit 41 reads the error ratio learning value Rqac n by looking up a map shown in FIG. 60 previously stored in the memory of the control unit 41, based on the engine rotation speed Ne and the target fuel injection amount Qsol.
  • the EGR flow velocity learning correction coefficient Kqac is calculated by adding 1 to the error ratio learning value Rqac n .
  • control unit 41 sets the EGR flow velocity learning correction coefficient Kqac to 1 in a step S262.
  • control unit 41 determines whether or not the learning permission flag felrn is 1.
  • step S264 the control unit 41 subtracts 1 from the EGR flow velocity feedback correction coefficient Kqac0 to calculate the current value Rqacp of the error ratio.
  • step S266 the learning value is updated using the subroutine of FIG. 61, and the subroutine is terminated.
  • control unit 41 When the learning permission flag felrn is not 1, in a step S265, the control unit 41 resets the current value Rqacp of the error ratio to 0, and terminates the subroutine of FIG. 50.
  • control unit 41 first reads the engine rotation speed Ne, target fuel injection amount Qsol and error ratio Rqacp calculated in the step S264.
  • a learning rate Tclrn is calculated by looking up a map shown in FIG. 62 previously stored in the memory of the control unit 41, based on the engine rotation speed Ne and target fuel injection amount Qsol.
  • the error ratio learning value Rqac n is calculated by looking up the aforesaid map of FIG. 60, based on the engine rotation speed Ne and target fuel injection amount Qsol.
  • step S354 weighted average processing by the following formula (22) is added to the error ratio Rqacp read in the step S351, and updating of the error ratio learning value is performed.
  • Rqac n (new ) Rqacp ⁇ Tclrn + Rqac n (old) ⁇ (1 - Tclrn ) where,
  • a next step S355 the stored value of the map of FIG. 60 is overwritten using the error ratio learning value Rqac n (new) calculated in this way.
  • control unit 41 terminates the processing of the step S12 of the main routine of FIG. 5.
  • control unit 41 performs the processing of a step S13.
  • the target EGR amount Tqek per cylinder of the diesel engine 1 is calculated by the following equation (23), using the target EGR amount Tqec calculated in the step S11, the flow velocity learning correction coefficient Kqac , the EGR flow velocity feedback correction coefficient Kqac0 , and the EGR amount feedback correction coefficient Kqac00 calculated in the step S12.
  • step S14 the delay processing value RVNTE of the target opening Rvnt is read.
  • the delay processing value RVNTE is a value obtained by adding delay processing by the routine shown in FIG. 63, performed in synchronism with the REF signal, to the target opening Rvnt calculated by the aforesaid routine of FIG. 25.
  • the control unit 41 reads the target opening Rvnt, and advance correction time constant equivalent value Tcvnt set in the step S144 of the subroutine in FIG. 29 for controlling turbocharging pressure.
  • the advance correction time constant equivalent value Tcvnt is a value for correcting the operating delay of the variable nozzle 53, as mentioned above.
  • the delay processing value RVNTE calculated by the formula (24) shows the actual opening of the variable nozzle 53 corresponding to the duty signal output to the pressure control valve 56 by the control unit 41.
  • the control unit 41 After reading the delay processing value RVNTE calculated in this way in the step S14 of FIG. 5, in a step S15, the control unit 41 calculates an opening area EAev per unit displacement by looking up a map shown in FIG. 64, based on the delay processing value RVNTE and the target EGR amount Tqek per cylinder of the diesel engine 1.
  • the delay processing value RVNTE which is the horizontal axis, may be considered to be approximately equal to the differential pressure upstream and downstream of the EGR valve 6.
  • the opening of the EGR valve 6 is set constant
  • the smaller the delay processing value RVNTE the larger the opening of the variable nozzle 53 and the higher the turbocharging pressure. Consequently, the differential pressure upstream and downstream of the EGR valve 6 becomes large.
  • the larger the delay processing value RVNTE the larger the opening of the variable nozzle 53 and the lower the turbocharging pressure. Consequently, the differential pressure upstream and downstream of the EGR valve 6 decreases.
  • the delay processing value RVNTE which is the horizontal axis may be considered to represent the differential pressure upstream and downstream of the EGR valve 6.
  • the opening of the EGR valve 6 can be specified with these parameters as can be understood from the map of FIG. 64.
  • FIG. 64 are temporary value assigned to show the relative magnitude of the opening of the EGR valve 6.
  • the inventors obtained the map of FIG. 64 by experiment, but the EGR valve opening area Aev may also be determined using a theoretically defined map as shown in FIG. 65.
  • the target EGR valve opening area Aev is calculated by multiplying EAev by the displacement SLOV# of the diesel engine 1 in a step S16, and the routine of FIG. 5 is terminated.
  • the target EGR valve opening area Aev obtained by the routine of FIG. 5 is converted for example to a lift amount or a drive signal of the EGR valve 6 using a map of FIG. 6.
  • the control unit 41 controls the opening of the EGR valve 6 to the target EGR valve opening area Aev by outputting a corresponding duty signal to the pressure control valve 5 which drives the EGR valve 6to realize the target EGR amount Tqek.
  • This invention calculates the target EGR valve opening area Aev taking the delay processing value RVNTE corresponding to the real opening of the variable nozzle 53 of the turbocharger 50 as a parameter. Therefore, EGR control of the diesel engine in the turbocharging state can be optimized by simple logic.
  • the pressure control valve 5 of the EGR valve 6 is controlled based on the target EGR valve opening area Aev , and if the pressure control valve 5 is changed to an electrical actuator, for example, provision can be made for the change-over to an actuator simply by replacing the map which converts the target EGR valve opening area Aev to the control signal of the pressure control valve 5, by a map which converts the target EGR valve opening area Aev to a control signal of the actuator.
  • the delay processing value RVNTE on the vertical axis and target EGR amount Tqek on the horizontal axis are both physical state amounts.
  • the target EGR valve opening area Aev can be adapted to any situation where these physical state amounts are known including transient states of the diesel engine 1.
  • the delay processing value RVNTE representing the real opening is further calculated by adding delay processing to the target opening Rvnt, and the target EGR valve opening area Aev is calculated based on the delay processing value RVNTE.
  • the size of the EGR valve 6 is usually selected to be directly proportional to the exhaust gas amount of the diesel engine 1, but according to this invention, the target EGR valve opening area Aev is calculated as the product of the target EGR valve opening area EAev per unit displacement volume and the piston displacement SLOV# , so it is easy to adapt to diesel engines having different displacements.
  • a routine shown in FIG. 16 is used instead of the routine of FIG. 15 for calculating the duty value Dtyvnt of the pressure control valve of the turbocharger.
  • the routine of FIG. 16 is also performed at an interval of 10 milliseconds.
  • the target opening Rvnt of the variable nozzle 53 was calculated based on the real EGR amount Qec , but in the routine of FIG. 16, the target opening Rvnt is calculated based on the real EGR rate Megrd.
  • the processing of the step S73 of FIG. 15 which calculates the real EGR amount Qec is omitted.
  • the routine shown in FIG. 27 is applied instead of the routine shown in FIG. 25 in the calculation of the target opening Rvnt of the variable nozzle 53.
  • the remaining processing details are identical to those of the first embodiment.
  • the control unit 41 reads the target intake air amount Qtac, real EGR rate Megrd, engine rotation speed Ne and target fuel injection amount Qsol.
  • a step S132 an identical calculation is performed to that of the step S122 of FIG. 15, and the intake air amount equivalent value tQas0 is calculated.
  • a step S133 the target opening Rvnt of the variable nozzle 53 is calculated by looking up a map shown in FIG. 28 previously stored in the memory of the control unit 41, based on the intake air amount equivalent value tQas0 and real EGR rate Megrd.
  • the vertical axis represents the EGR rate equivalent value Qes0 , but in the map of FIG. 28, the vertical axis represents the real EGR rate Megrd.
  • the two maps differ only with regard to these parameters, and the characteristics of the target opening Rvnt obtained are identical whichever map is used.
  • the map used to calculate the target opening Rvnt may be specified using various parameters in addition to the above. For example, in the map of FIG. 26, instead of the EGR amount equivalent value Qes0 on the vertical axis, the real EGR amount Qec or the EGR amount Qec0 per cylinder at the inlet of the collector 3A may be taken. In a map of FIG. 28, instead of the intake air amount equivalent value tQas0 on the horizontal axis, the target intake air amount tQac may be taken. Further, instead of the real EGR rate Megrd on the vertical axis, the target EGR rate Megr may be taken.
  • the target EGR valve opening area Aev was calculated using the delay processing value RVNTE corresponding to the real opening of the variable nozzle 53 of the turbocharger 50 as a parameter, but it will be understood that it is also within the scope of the invention to detect the real opening of the variable nozzle 53 by a sensor, and to calculate the target EGR valve opening area Aev using the detected real opening as a parameter. If the variable nozzle 53 is driven by a step motor, the step number of the step motor may be used as a representative value for the real opening of the variable nozzle 53..
  • the turbocharging pressure is varied by varying the surface area across which the exhaust gas passes. Therefore, in addition to the variable nozzle, the turbocharging pressure can be varied also by varying the opening of a scroll or diffuser.
  • This type of variable capacity turbocharger is referred to as a variable geometric turbocharger.
  • the target EGR valve opening area Aev can be calculated based on the substantial cross-sectional area of the exhaust gas passage of the exhaust gas turbine as a parameter.
  • the turbocharging pressure may be varied by opening and closing the waste gate valve.
  • the pressure variation may be converted into a variation of an apparent cross-sectional area of the exhaust gas passage, and the target EGR valve opening area Aev calculated using the converted value as a parameter.

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  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
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EP01111467A 2000-05-12 2001-05-10 Regelung für einen Dieselmotor Expired - Lifetime EP1154139B1 (de)

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US6606981B2 (en) 2003-08-19
US20010045210A1 (en) 2001-11-29
DE60107996D1 (de) 2005-02-03
JP2001323824A (ja) 2001-11-22
EP1154139A3 (de) 2003-03-19
EP1154139B1 (de) 2004-12-29
DE60107996T2 (de) 2005-05-19

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